Final answer:
1) Preventing infection is the priority action by the nurse when implementing the neonate's plan of care for a myelomeningocele.
Step-by-step explanation:
The priority action by the nurse when implementing the neonate's plan of care for a myelomeningocele is preventing infection. This is because an open neural tube defect such as a myelomeningocele puts the neonate at a high risk of infection. The nurse should ensure strict sterile techniques during dressing changes, monitor for signs of infection, and administer prophylactic antibiotics as prescribed by the healthcare provider.